﻿using UnityEngine;
using System.Collections;
using System;

public class PUNoise3D
{
	protected static int[] permutation = { 151,160,137,91,90,15,
		131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
		190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
		88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
		77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
		102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
		135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
		5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
		223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
		129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
		251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
		49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
		138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
	};

	public PUNoise3D ()
	{
		_p = new int[512];
		_octaves = 2;
		_frequency = 1.0;
		_amplitude = 1.0;
		_persistence = 1.0f;
	}
	
	/* Inititialises the noise function */
	public void initialise(uint octaves, double frequency = 1.0, double amplitude = 1.0, double persistence = 1.0)
	{
		_octaves = octaves;
		_frequency = frequency;
		_amplitude = amplitude;
		_persistence = persistence;
		
		for (int i = 0; i < 256; ++i)
		{
			_p[i] = permutation[i];
			_p[256+i] = permutation[i];
		}
	}

	/* Returns a noise value between [0, 1]
    @remarks
        The noise is calculated in realtime
    */
	public double noise(double x, double y, double z)
	{
		double n = 0;
		double freq = _frequency;
		double ampl = _amplitude;
		for (uint u = 0; u < _octaves; ++u) 
		{ 
			n += genNoise(x * freq, y * freq, z * freq) * ampl;
			freq *= 2;
			ampl *= _persistence;
		}
		return n;
	}
	
	/* Returns a noise value between [0, 1]
    @remarks
        The noise is calculated in realtime
    */
	public double noise(Vector3 position)
	{
		return noise(position.x, position.y, position.z);
	}
	
	protected double genNoise(double x, double y, double z)
	{
		int X = (int)Math.Floor(x) & 255;
		int Y = (int)Math.Floor(y) & 255;
		int Z = (int)Math.Floor(z) & 255;
		x -= Math.Floor(x);
		y -= Math.Floor(y);
		z -= Math.Floor(z);
		double u = fade(x);
		double v = fade(y);
		double w = fade(z);
		int A = _p[X  ]+Y, AA = _p[A]+Z, AB = _p[A+1]+Z;
		int B = _p[X+1]+Y, BA = _p[B]+Z, BB = _p[B+1]+Z;
		
		double lrp = lerp(w,	lerp(v, lerp(u, grad(_p[AA], x, y, z),
		                                  grad(_p[BA], x-1, y, z)),
		                          lerp(u, grad(_p[AB], x, y-1, z),
		     grad(_p[BB], x-1, y-1, z))),
		                  lerp(v, lerp(u, grad(_p[AA+1], x, y  , z-1),
		             grad(_p[BA+1], x-1, y, z-1)),
		     lerp(u, grad(_p[AB+1], x, y-1, z-1),
		     grad(_p[BB+1], x-1, y-1, z-1))));
		return Math.Abs(lrp); // Use absolute value, because lrp in between [-1, 1]
	}
	
	protected double fade(double t)
	{
		return t * t * t * (t * (t * 6 - 15) + 10);
	}

	protected double lerp(double t, double a, double b)
	{
		return a + t * (b - a);
	}

	protected double grad(int hash, double x, double y, double z)
	{
		int h = hash & 15;
		double u = h<8 ? x : y;
		double v = h<4 ? y : h==12||h==14 ? x : z;
		return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
	}
	
	protected int[] _p;
	protected uint _octaves;
	protected double _frequency;
	protected double _amplitude;
	protected double _persistence;

};
